Electrochromic device having a seal including an epoxy resin cured with a cycloaliphatic amine

ABSTRACT

An electrochromic variable reflectance mirror for a vehicle includes a front element and a rear element. A seal is provided to sealably bond the elements together in a spaced-apart relationship to define a chamber, and an electrochromic material is disposed in the chamber. The seal comprises an epoxy resin cured with a cycloaliphatic amine. The cycloaliphatic amine may be a bis(cycloaliphatic) amine, or more specifically, bis(aminocyclohexyl) methane (PACM). The epoxy resin may be an epoxy novolac resin such as an epoxy phenolic novolac (e.g., DEN431) or an epoxy cresyl novolac resin, a bisphenol A epoxy resin, a bisphenol F epoxy resin, a tetraglycidyl methylenebisbenzenamine, or a glycidyl benzenamine.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of co-pending U.S. patentapplication Ser. No. 09/994,218, entitled “ELECTROCHROMIC REARVIEWMIRROR INCORPORATING A THIRD SURFACE PARTIALLY TRANSMISSIVE REFLECTOR,”filed on Nov. 26, 2001, by William L. Tonar et al.; which is acontinuation of U.S. patent application Ser. No. 09/311,955, filed onMay 14, 1999, entitled “ELECTROCHROMIC REARVIEW MIRROR INCORPORATING ATHIRD SURFACE METAL REFLECTOR AND A DISPLAY/SIGNAL LIGHT,” by William L.Tonar et al., now U.S. Pat. No. 6,356,376; which is acontinuation-in-part of U.S. patent application Ser. No. 09/206,788,filed on Dec. 7, 1998, entitled “ELECTROCHROMIC REARVIEW MIRRORINCORPORATING A THIRD SURFACE METAL REFLECTOR AND A DISPLAY/SIGNALLIGHT,” by William L. Tonar et al., now U.S. Pat. No. 6,166,848; whichis a continuation-in-part of co-pending U.S. patent application Ser. No.09/197,400, filed on Nov. 20, 1998, entitled “ELECTROCHROMIC REARVIEWMIRROR INCORPORATING A THIRD SURFACE METAL REFLECTOR AND ADISPLAY/SIGNAL LIGHT,” by William L. Tonar et al., now U.S. Pat. No.6,111,684; which is a continuation-in-part of U.S. patent applicationSer. No. 09/114,386, entitled “ELECTROCHOMIC REARVIEW MIRRORINCORPORATING A THIRD SURFACE METAL REFLECTOR,” filed on Jul. 13, 1998by Jeffrey A. Forgette et al., now U.S. Pat. No. 6,064,508; which is acontinuation of U.S. patent application Ser. No. 08/832,587, entitled“ELECTROCHOMIC REARVIEW MIRROR INCORPORATING A THIRD SURFACE METALREFLECTOR,” filed on Apr. 2, 1997, by Jeffrey A. Forgette et al., nowU.S. Pat. No. 5,818,625. Priority under 35 U.S.C. §120 is hereby claimedas to the filing dates of each of these applications. The entiredisclosures of each of these applications are incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] This invention relates to electrochromic rearview mirrors formotor vehicles and, more particularly, to improved electrochromicrearview mirrors incorporating third surface reflector/electrode incontact with at least one solution-phase electrochromic material.

[0003] Heretofore, various rearview mirrors for motor vehicles have beenproposed which change from the full reflectance mode (day) to thepartial reflectance mode(s) (night) for glare-protection purposes fromlight emanating from the headlights of vehicles approaching from therear. Among such devices are those wherein the transmittance is variedby thermochromic, photochromic, or electro-optic (e.g., liquid crystal,dipolar suspension, electrophoretic, electrochromic, etc.) means andwhere the variable transmittance characteristic affects electromagneticradiation that is at least partly in the visible spectrum (wavelengthsfrom about 3800 Å to about 7800 Å). Devices of reversibly variabletransmittance to electromagnetic radiation have been proposed as thevariable transmittance element in variable transmittance light filters,variable reflectance mirrors, and display devices which employ suchlight filters or mirrors in conveying information. These variabletransmittance light filters have included windows.

[0004] Devices of reversibly variable transmittance to electromagneticradiation, wherein the transmittance is altered by electrochromic means,are described, for example, by Chang, “Electrochromic andElectrochemichromic Materials and Phenomena,” in Non-emissiveElectrooptic Displays, A. Kmetz and K. von Willisen, eds. Plenum Press,New York, N.Y. 1976, pp. 155-196 (1976) and in various parts ofEletrochromism, P. M. S. Monk, R. J. Mortimer, D. R. Rosseinsky, VCHPublishers, Inc., New York, N.Y. (1995). Numerous electrochromic devicesare known in the art. See, e.g., Manos, U.S. Pat. No. 3,451,741;Bredfeldt et al., U.S. Pat. No. 4,090,358; Clecak et al., U.S. Pat. No.4,139,276; Kissa et al., U.S. Pat. No. 3,453,038; Rogers, U.S. Pat. Nos.3,652,149, 3,774,988 and 3,873,185; and Jones et al., U.S. Pat. Nos.3,282,157, 3,282,158, 3,282,160 and 3,283,656.

[0005] In addition to these devices there are commercially availableelectrochromic devices and associated circuitry, such as those disclosedin U.S. Pat. No. 4,902,108, entitled “SINGLE-COMPARTMENT, SELF-ERASING,SOLUTION-PHASE ELECTROCHROMIC DEVICES SOLUTIONS FOR USE THEREIN, ANDUSES THEREOF”, issued Feb. 20, 1990, to Harlan J. Byker; Canadian PatentNo. 1,300,945, entitled “AUTOMATIC REARVIEW MIRROR SYSTEM FOR AUTOMOTIVEVEHICLES,” issued May 19, 1992, to Jon H. Bechtel et al.; U.S. Pat. No.5,128,799, entitled “VARIABLE REFLECTANCE MOTOR VEHICLE MIRROR,” issuedJul. 7, 1992, to Harlan J. Byker; U.S. Pat. No. 5,202,787, entitled“ELECTRO-OPTIC DEVICE”, issued Apr. 13, 1993, to Harlan J. Byker et al.;U.S. Pat. No. 5,204,778, entitled “CONTROL SYSTEM FOR AUTOMATIC REARVIEWMIRRORS,” issued Apr. 20, 1993, to Jon H. Bechtel; U.S. Pat. No.5,278,693, entitled “TINTED SOLUTION-PHASE ELECTROCHROMIC MIRRORS,”issued Jan. 11, 1994, to David A. Theiste et al.; U.S. Pat. No.5,280,380, entitled “UV-STABILIZED COMPOSITIONS AND METHODS,” issuedJan. 18, 1994, to Harlan J. Byker; U.S. Pat. No. 5,282,077, entitled“VARIABLE REFLECTANCE MIRROR,” issued Jan. 25, 1994, to Harlan J. Byker;U.S. Pat. No. 5,294,376, entitled “BIPYRIDINIUM SALT SOLUTIONS,” issuedMar. 15, 1994, to Harlan J. Byker; U.S. Pat. No. 5,336,448, entitled“ELECTROCHROMIC DEVICES WITH BIPYRIDINIUM SALT SOLUTIONS,” issued Aug.9, 1994, to Harlan J. Byker; U.S. Pat. No. 5,434,407, entitled“AUTOMATIC REARVIEW MIRROR INCORPORATING LIGHT PIPE,” issued Jan. 18,1995, to Frederick T. Bauer et al.; U.S. Pat. No. 5,448,397, entitled“OUTSIDE AUTOMATIC REARVIEW MIRROR FOR AUTOMOTIVE VEHICLES,” issued Sep.5, 1995, to William L. Tonar; and U.S. Pat. No. 5,451,822, entitled“ELECTRONIC CONTROL SYSTEM,” issued Sep. 19, 1995, to Jon H. Bechtel etal. Each of these patents is commonly assigned with the presentinvention and the disclosures of each, including the referencescontained therein, are hereby incorporated herein in their entirety byreference. Such electrochromic devices may be utilized in a fullyintegrated inside/outside rearview mirror system or as separate insideor outside rearview mirror systems.

[0006]FIG. 1 shows a typical electrochromic mirror device 10, havingfront and rear planar elements 12 and 16, respectively. A transparentconductive coating 14 is placed on the rear face of the front element12, and another transparent conductive coating 18 is placed on the frontface of rear element 16. A reflector (20 a, 20 b and 20 c), typicallycomprising a silver metal layer 20 a covered by a protective coppermetal layer 20 b, and one or more layers of protective paint 20 c, isdisposed on the rear face of the rear element 16. For clarity ofdescription of such a structure, the front surface of the front glasselement is sometimes referred to as the first surface, and the insidesurface of the front glass element is sometimes referred to as thesecond surface. The inside surface of the rear glass element issometimes referred to as the third surface, and the back surface of therear glass element is sometimes referred to as the fourth surface. Thefront and rear elements are held in a parallel and spaced-apartrelationship by seal 22, thereby creating a chamber 26. Theelectrochromic medium 24 is contained in space 26. The electrochromicmedium 24 is in direct contact with transparent electrode layers 14 and18, through which passes electromagnetic radiation whose intensity isreversibly modulated in the device by a variable voltage or potentialapplied to electrode layers 14 and 18 through clip contacts and anelectronic circuit (not shown).

[0007] The electrochromic medium 24 placed in space 26 may includesurface-confined, electrodeposition type or solution-phase typeelectrochromic materials and combinations thereof. In an allsolution-phase medium, the electrochemical properties of the solvent,optional inert electrolyte, anodic materials, cathodic materials, andany other components that might be present in the solution arepreferably such that no significant electrochemical or other changesoccur at a potential difference which oxidizes anodic material andreduces the cathodic material other than the electrochemical oxidationof the anodic material, electrochemical reduction of the cathodicmaterial and the self-erasing reaction between the oxidized form of theanodic material and the reduced form of the cathodic material.

[0008] In most cases, when there is no electrical potential differencebetween transparent conductors 14 and 18, the electrochromic medium 24in space 26 is essentially colorless or nearly colorless, and incominglight (I_(O)) enters through front element 12, passes throughtransparent coating 14, electrochromic containing chamber 26,transparent coating 18, rear element 16, and reflects off layer 20 a andtravels back through the device and out front element 12. Typically, themagnitude of the reflected image (I_(R)) with no electrical potentialdifference is about 45 percent to about 85 percent of the incident lightintensity (I_(O)). The exact value depends on many variables outlinedbelow, such as, for example, the residual reflection (I′_(R)) from thefront face of the front element, as well as secondary reflections fromthe interfaces between: the front element 12 and the front transparentelectrode 14; the front transparent electrode 14 and the electrochromicmedium 24; the electrochromic medium 24 and the second transparentelectrode 18; and the second transparent electrode 18 and the rearelement 16. These reflections are well known in the art and are due tothe difference in refractive indices between one material and another asthe light crosses the interface between the two. If the front elementand the back element are not parallel, then the residual reflectance(I′_(R)) or other secondary reflections will not superimpose with thereflected image (I_(R)) from mirror surface 20 a, and a double imagewill appear (where an observer would see what appears to be double (ortriple) the number of objects actually present in the reflected image).

[0009] There are minimum requirements for the magnitude of the reflectedimage depending on whether the electrochromic mirrors are placed on theinside or the outside of the vehicle. For example, according to currentrequirements from most automobile manufacturers, inside mirrors musthave a high-end reflectivity of at least 70 percent and outside mirrorsmust have a high-end reflectivity of at least 50 percent.

[0010] Electrode layers 14 and 18 are connected to electronic circuitrywhich is effective to electrically energize the electrochromic medium,such that when a potential is applied across the transparent conductors14 and 18, electrochromic medium in space 26 darkens such that incidentlight (I_(O)) is attenuated as the light passes toward the reflector 20a and as it passes back through after being reflected. By adjusting thepotential difference between the transparent electrodes, such a devicecan function as a “gray-scale” device, with continuously variabletransmittance over a wide range. For solution-phase electrochromicsystems, when the potential between the electrodes is removed orreturned to zero, the device spontaneously returns to the same,zero-potential, equilibrium color and transmittance as the device hadbefore the potential was applied. Other electrochromic materials areavailable for making electrochromic devices. For example, theelectrochromic medium may include electrochromic materials that aresolid metal oxides, redox active polymers and hybrid combinations ofsolution-phase and solid metal oxides or redox active polymers; however,the above-described solution-phase design is typical of most of theelectrochromic devices presently in use.

[0011] Even before a fourth surface reflector electrochromic mirror wascommercially available, various groups researching electrochromicdevices had discussed moving the reflector from the fourth surface tothe third surface. Such a design has advantages in that it should,theoretically, be easier to manufacture because there are fewer layersto build into a device, i.e., the third surface transparent electrode isnot necessary when there is a third surface reflector/electrode.Although this concept was described as early as 1966, no group hadcommercial success because of the exacting criteria demanded from aworkable auto-dimming mirror incorporating a third surface reflector.U.S. Pat. No. 3,280,701, entitled “OPTICALLY VARIABLE ONE-WAY MIRROR,”issued Oct. 25, 1966, to J. F. Donnelly et al. has one of the earliestdiscussions of a third surface reflector for a system using a pH-inducedcolor change to attenuate light.

[0012] U.S. Pat. No. 5,066,112, entitled “PERIMETER COATED,ELECTRO-OPTIC MIRROR,” issued Nov. 19, 1991, to N. R. Lynam et al.teaches an electro-optic mirror with a conductive coating applied to theperimeter of the front and rear glass elements for concealing the seal.Although a third surface reflector is discussed therein, the materialslisted as being useful as a third surface reflector suffer from one ormore of the following deficiencies: not having sufficient reflectivityfor use as an inside mirror, or not being stable when in contact with asolution-phase electrochromic medium containing at least onesolution-phase electrochromic material.

[0013] Others have broached the topic of a reflector/electrode disposedin the middle of all solid state-type devices. For example, U.S. Pat.Nos. 4,762,401, 4,973,141, and 5,069,535 to Baucke et al. teach anelectrochromic mirror having the following structure: a glass element; atransparent (ITO) electrode; a tungsten oxide electrochromic layer; asolid ion-conducting layer; a single layer hydrogen ion-permeablereflector; a solid ion conducting layer; a hydrogen ion storage layer; acatalytic layer; a rear metallic layer; and a back element (representingthe conventional third and fourth surface). The reflector is notdeposited on the third surface and is not directly in contact withelectrochromic materials, certainly not at least one solution-phaseelectrochromic material and associated medium.

[0014] Consequently, it is desirable to provide an improved highreflectivity electrochromic rearview mirror having a third surfacereflector/electrode in contact with a solution-phase electrochromicmedium containing at least one electrochromic material.

SUMMARY OF THE INVENTION

[0015] Aspects of the present invention, which will become apparent fromthe specification as a whole, including the drawings, are accomplishedin accordance with the present invention by incorporating areflector/electrode on the inside (third) surface of a dimming portionof the rearview mirror. This reflector/electrode forms an integralelectrode in contact with at least one solution-phase electrochromicmaterial, and may be a single layer of a highly reflective silver alloyor may comprise a series of coatings where the outer coating is a highlyreflective silver alloy. When a series of coatings is used for thereflector/electrode, there should be a base coating which bonds to theglass surface and resists any adverse interaction, e.g., corrosiveaction, with any constituents of the electrochromic medium, an optionalintermediate layer (or layers) which bonds well to the base coating andresists any adverse interaction with the electrochromic medium, and atleast one highly reflective silver alloy which directly contacts theelectrochromic medium and which is chosen primarily for its adequatebond to the peripheral seal, its high reflectance, good shelf life,stable behavior as an electrode, resistance to adverse interaction withthe electrochromic medium, resistance to atmospheric corrosion,resistance to electrical contact corrosion, and the ability to adhere tothe base or intermediate layer(s), if present. If a single layer ofhighly reflective silver alloy is utilized, it must also meet theseoperational criteria.

[0016] In another embodiment of the present invention, when a very thinover-coating is placed over the highly reflective layer, then the highlyreflective layer may be silver metal or a silver alloy.

[0017] In yet another embodiment of the present invention, the thirdsurface reflector/electrode includes at least one base layer that isdisposed over the entire third surface of the electrochromic mirror. Ahighly reflective layer is disposed over the central portion of the baselayer(s) and not over the perimeter edge portion where the seal will beplaced. Optionally, one or more intermediate layers may be disposedbetween the base and reflective layers, and may be placed over theentire third surface, or may be placed over the central portion or both(if there is more than one intermediate layer).

[0018] The third surface reflector of the present invention mayadditionally provide for significant improvement of the electricalinterconnection techniques used to impart a voltage or drive potentialto the transparent conductor on the second surface of the electrochromicmirror. This is accomplished both by providing improved contactstability between the contacts, such as clips, and the reflector layerand by providing unique and advantageous buss bar configurations.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The subject matter that is regarded as the invention isparticularly pointed out and distinctly claimed in the concludingportion of the specification. The invention, together with furtherobjects and advantages thereof, may best be understood by reference tothe following description taken in connection with the accompanyingdrawings, where like numerals represent like components, in which:

[0020]FIG. 1 is an enlarged cross-sectional view of a prior artelectrochromic mirror assembly;

[0021]FIG. 2 is a front elevational view schematically illustrating aninside/outside electrochromic rearview mirror system for motor vehicleswhere the inside and outside mirrors incorporate the mirror assembly ofthe present invention;

[0022]FIG. 3 is an enlarged cross-sectional view of the insideelectrochromic rearview mirror incorporating a third surfacereflector/electrode illustrated in FIG. 2, taken on the line 2-2′thereof;

[0023]FIG. 4 is an enlarged cross-sectional view of an electrochromicmirror incorporating an alternate embodiment of a third surfacereflector/electrode according to the present invention;

[0024]FIG. 5a is an enlarged cross-sectional view of an electrochromicmirror having an improved arrangement for applying a drive potential tothe transparent conductor on the second surface of the mirror;

[0025]FIG. 5b is an enlarged top view of the third surface reflector ofFIG. 5a; and

[0026]FIG. 6 is an enlarged cross-sectional view of an electrochromicmirror using a cured and machine-milled epoxy seal to hold thetransparent elements in a spaced-apart relationship.

DETAILED DESCRIPTION OF THE INVENTION

[0027]FIG. 2 shows a front elevational view schematically illustratingan inside mirror assembly 110 and two outside rearview mirror assemblies111 a and 111 b for the driver-side and passenger-side, respectively,all of which are adapted to be installed on a motor vehicle in aconventional manner and where the mirrors face the rear of the vehicleand can be viewed by the driver of the vehicle to provide a rearwardview. Inside mirror assembly 110, and outside rearview mirror assemblies111 a and 111 b may incorporate light-sensing electronic circuitry ofthe type illustrated and described in the above-referenced CanadianPatent No. 1,300,945, U.S. Pat. No. 5,204,778, or U.S. Pat. No.5,451,822, and other circuits capable of sensing glare and ambient lightand supplying a drive voltage to the electrochromic element. Mirrorassemblies 110, 111 a, and 111 b are essentially identical in that likenumbers identify components of the inside and outside mirrors. Thesecomponents may be slightly different in configuration but function insubstantially the same manner and obtain substantially the same resultsas similarly numbered components. For example, the shape of the frontglass element of inside mirror 110 is generally longer and narrower thanoutside mirrors 111 a and 111 b. There are also some differentperformance standards placed on inside mirror 110 compared with outsidemirrors 111 a and 111 b. For example, inside mirror 110 generally, whenfully cleared, should have a reflectance value of about 70 percent toabout 85 percent or higher whereas the outside mirrors often have areflectance of about 50 percent to about 65 percent. Also, in the UnitedStates (as supplied by the automobile manufacturers), the passenger-sidemirror 111 b typically has a spherically bent, or convex shape, whereasthe driver-side mirror 111 a and inside mirror 110 presently must beflat. In Europe the driver-side mirror 111 a is commonly flat oraspheric, whereas the passenger-side mirror 111 b has a convex shape. InJapan, both outside mirrors have a convex shape. The followingdescription is generally applicable to all mirror assemblies of thepresent invention.

[0028]FIG. 3 shows a cross-sectional view of mirror assembly 110 havinga front transparent element 112 having a front surface 112 a and a rearsurface 112 b, and a rear element 114 having a front surface 114 a and arear surface 114 b. For clarity of description of such a structure, thefollowing designations will be used hereinafter. The front surface 112 aof the front glass element will be referred to as the first surface andthe back surface 112 b of the front glass element as the second surface.The front surface 114 a of the rear glass element will be referred to asthe third surface, and the back surface 114 b of the rear glass elementas the fourth surface. Chamber 125 is defined by a layer of transparentconductor 128 (disposed on second surface 112 b), a reflector/electrode120 (disposed on third surface 114 a), and an inner circumferential wall132 of sealing member 116.

[0029] Front transparent element 112 may be any material which istransparent and has sufficient strength to be able to operate in theconditions, e.g., varying temperatures and pressures, commonly found inthe automotive environment. Front element 112 may comprise any type ofborosilicate glass, soda lime glass, float glass or any other material,such as, for example, a polymer or plastic, that is transparent in thevisible region of the electromagnetic spectrum. Front element 112 ispreferably a sheet of glass. Rear element 114 must meet the operationalconditions outlined above, except that it does not need to betransparent, and therefore may comprise polymers, metals, glass,ceramics, and preferably is a sheet of glass.

[0030] The coatings of the third surface 114 a are sealably bonded tothe coatings on the second surface 112 b in a spaced-apart and parallelrelationship by a seal member 116 disposed near the outer perimeter ofboth second surface 112 b and third surface 114 a. Seal member 116 maybe any material that is capable of adhesively bonding the coatings onthe second surface 112 b to the coatings on the third surface 114 a toseal the perimeter such that electrochromic material 126 does not leakfrom chamber 125. Optionally, the layer of transparent conductivecoating 128 and the layer of reflector/electrode 120 may be removed overa portion where the seal member is disposed (not the entire portion,otherwise the drive potential could not be applied to the two coatings).In such a case, seal member 116 must bond well to glass.

[0031] The performance requirements for a perimeter seal member 116 usedin an electrochromic device are similar to those for a perimeter sealused in a liquid crystal device (LCD) which are well known in the art.The seal must have good adhesion to glass, metals and metal oxides; musthave low permeabilities for oxygen, moisture vapor and other detrimentalvapors and gases; and must not interact with or poison theelectrochromic or liquid crystal material it is meant to contain andprotect. The perimeter seal can be applied by means commonly used in theLCD industry such as by silk-screening or dispensing. Totally hermeticseals such as those made with glass frit or solder glass can be used,but the high temperatures involved in processing (usually near 450° C.)this type of seal can cause numerous problems such as glass substratewarpage, changes in the properties of transparent conductive electrode,and oxidation or degradation of the reflector. Because of their lowerprocessing temperatures, thermoplastic, thermosetting, or UV curingorganic sealing resins are preferred. Such organic resin sealing systemsfor LCDs are described in U.S. Pat. Nos. 4,297,401, 4,418,102,4,695,490, 5,596,023 and 5,596,024. Because of their excellent adhesionto glass, low oxygen permeability, and good solvent resistance, epoxybased organic sealing resins are preferred. These epoxy resin seals maybe UV curing, such as described in U.S. Pat. No. 4,297,401, or thermallycuring, such as with mixtures of liquid epoxy resin with liquidpolyamide resin or dicyandiamide, or they can be homopolymerized. Theepoxy resin may contain fillers or thickeners to reduce flow andshrinkage such as fumed silica, silica, mica, clay, calcium carbonate,alumina, etc., and/or pigments to add color. Fillers pretreated withhydrophobic or silane surface treatments are preferred. Cured resincrosslink density can be controlled by use of mixtures ofmono-functional, di-functional, and multi-functional epoxy resins andcuring agents. Additives such as silanes or titanates can be used toimprove the seal's hydrolytic stability, and spacers such as glass beadsor rods can be used to control final seal thickness and substratespacing. Suitable epoxy resins for use in a perimeter seal member 116include but are not limited to: “EPON RESIN” 813, 825, 826, 828, 830,834, 862, 1001F, 1002F, 2012, DPS-155, 164, 1031, 1074, 58005, 58006,58034, 58901, 871, 872 and DPL-862 available from Shell Chemical Co.,Houston, Tex.; “ARALITE” GY 6010, GY 6020, CY 9579, GT 7071, XU 248, EPN1139, EPN 1138, PY 307, ECN 1235, ECN 1273, ECN 1280, MT 0163, MY 720,MY 0500, MY 0510 and PT 810 available from Ciba Geigy, Hawthorne, N.Y.;“D.E.R.” 331, 317, 361, 383, 661, 662, 667, 732, 736, “D.E.N.” 431, 438,439 and 444 available from Dow Chemical Co., Midland, Mich. Suitableepoxy curing agents include V-15, V-25 and V-40 polyamides from ShellChemical Co.; “AJICURE” PN-23, PN-34 and VDH available from AjinomotoCo., Tokyo, Japan; “CUREZOL” AMZ, 2MZ, 2E4MZ, C11Z, C17Z, 2PZ, 21Z and2P4MZ available from Shikoku Fine Chemicals, Tokyo, Japan; “ERISYS” DDAor DDA accelerated with U-405, 24EMI, U-410 and U-415 available from CVCSpecialty Chemicals, Maple Shade, N.J.; “AMICURE” PACM, 352, CG, CG-325and CG-1200 available from Air Products, Allentown, Pa. Suitable fillersinclude fumed silica such as “CAB-O-SIL” L-90, LM-130, LM-5, PTG, M-5,MS-7, MS-55, TS-720, HS-5, EH-5 available from Cabot Corporation,Tuscola, Ill.; “AEROSIL” R972, R974, R805, R812, R812 S, R202, US204 andUS206 available from Degussa, Akron, Ohio. Suitable clay fillers includeBUCA, CATALPO, ASP NC, SATINTONE 5, SATINTONE SP-33, TRANSLINK 37,TRANSLINK 77, TRANSLINK 445, TRANSLINK 555 available from EngelhardCorporation, Edison, N.J. Suitable silica fillers are SILCRON G-130,G-300, G-100-T and G-100 available from SCM Chemicals, Baltimore, Md.Suitable silane coupling agents to improve the seal's hydrolyticstability are Z-6020, Z-6030, Z-6032, Z-6040, Z-6075 and Z-6076available from Dow Corning Corporation, Midland, Mich. Suitableprecision glass microbead spacers are available in an assortment ofsizes from Duke Scientific, Palo Alto, Calif.

[0032] The layer of a transparent electrically conductive material 128is deposited on the second surface 112 b to act as an electrode.Transparent conductive material 128 may be any material which bonds wellto front element 112, is resistant to corrosion to any materials withinthe electrochromic device, resistant to corrosion by the atmosphere, hasminimal diffuse or specular reflectance, high light transmission, nearneutral coloration and good electrical conductance. Transparentconductive material 128 may be fluorine doped tin oxide, tin dopedindium oxide (ITO), ITO/metal/ITO (IMI) as disclosed in “TransparentConductive Multilayer-Systems for FPD Applications”, by J. Stollenwerk,B. Ocker, K. H. Kretschmer of LEYBOLD AG, Alzenau, Germany, and thematerials described in above-referenced U.S. Pat. No. 5,202,787, such asTEC 20 or TEC 15, available from Libbey Owens-Ford Co. of Toledo, Ohio.Generally, the conductance of transparent conductive material 128 willdepend on its thickness and composition. IMI generally has superiorconductivity compared with the other materials. IMI, however, is moredifficult and expensive to manufacture and may be useful when highconductance is necessary. The thickness of the various layers in the IMIstructure may vary but generally the thickness of the first ITO layerranges from about 10 Å to about 200 Å, the metal ranges from about 10 Åto about 200 Å, and the second layer of ITO ranges from about 10 Å toabout 200 Å. If desired, an optional layer or layers of a colorsuppression material 130 may be deposited between transparent conductivematerial 128 and the second surface 112 b to suppress the reflection ofany unwanted portions of the electromagnetic spectrum.

[0033] In accordance with the present invention, a combinationreflector/electrode 120 is disposed on third surface 114 a.Reflector/electrode 120 comprises at least one layer of a highlyreflective material 121 which serves as a mirror reflectance layer andalso forms an integral electrode in contact with and in a chemically andelectrochemically stable relationship with any constituents in anelectrochromic medium. As stated above, the conventional method ofbuilding electrochromic devices was to incorporate a transparentconductive material on the third surface as an electrode, and place areflector on the fourth surface. By combining the “reflector” and“electrode,” and placing both on the third surface, several unexpectedadvantages arise, which not only make the device manufacture lesscomplex, but also allow the device to operate with higher performance.The following will outline the exemplary advantages of the combinedreflector/electrode of the present invention.

[0034] First, the combined reflector/electrode 120 on the third surfacegenerally has a higher conductance than a conventional transparentelectrode and previously used reflector/electrodes which will allowgreater design flexibility. One can change the composition of thetransparent conductive electrode on the second surface to one that haslower conductance (being cheaper and easier to produce and manufacture)while maintaining coloration speeds similar to that obtainable with afourth surface reflector device, while at the same time decreasingsubstantially the overall cost and time to produce the electrochromicdevice. If, however, performance of a particular design is of utmostimportance, a moderate to high conductance transparent electrode can beused on the second surface, such as, for example, ITO, IMI, etc. Thecombination of a high conductance reflector/electrode on the thirdsurface and a high conductance transparent electrode on the secondsurface will not only produce an electrochromic device with more evenoverall coloration, but will also allow for increased speed ofcoloration and clearing. Furthermore, in fourth surface reflector mirrorassemblies there are two transparent electrodes with relatively lowconductance and in previously used third surface reflector mirrors thereis a transparent electrode and a reflector/electrode with relatively lowconductance and, as such, a long buss bar on the front and rear elementto bring current in and out is necessary to ensure adequate coloringspeed. The third surface reflector/electrode of the present inventionhas a higher conductance and therefore has a very even voltage orpotential distribution across the conductive surface, even with a smallor irregular contact area. Thus, the present invention provides greaterdesign flexibility by allowing the electrical contact for the thirdsurface electrode to be very small while still maintaining adequatecoloring speed.

[0035] Second, a third surface reflector/electrode helps improve theimage being viewed through the mirror. FIG. 1 shows how light travelsthrough a conventional fourth surface reflector device. In the fourthsurface reflector the light travels through: the first glass element;the transparent conductive electrode on the second surface; theelectrochromic media; the transparent conductive electrode on the thirdsurface; and the second glass element, before being reflected by thefourth surface reflector. Both transparent conductive electrodes exhibithighly specular transmittance but also possess diffuse transmittance andreflective components, whereas the reflective layer utilized in anyelectrochromic mirror is chosen primarily for its specular reflectance.By diffuse reflectance or transmittance component we mean a materialwhich reflects or transmits a portion of any light impinging on itaccording to Lambert's law whereby the light rays are spread about orscattered. By specular reflectance or transmittance component we mean amaterial which reflects or transmits light impinging on it according toSnell's laws of reflection or refraction. In practical terms, diffusereflectors and transmitters tend to slightly blur images, whereasspecular reflectors show a crisp, clear image. Therefore, lighttraveling through a mirror having a device with a fourth surfacereflector has two partial diffuse reflectors (on the second and thirdsurface) which tend to blur the image, and a device with a third surfacereflector/electrode of the present invention only has one diffusereflector (on the second surface).

[0036] Additionally, because the transparent electrodes act as partialdiffuse transmitters, and the farther away the diffuse transmitter isfrom the reflecting surface the more severe the blurring becomes, amirror with a fourth surface reflector appears significantly more hazythan a mirror with a third surface reflector. For example, in the fourthsurface reflector shown in FIG. 1, the diffuse transmitter on the secondsurface is separated from the reflector by the electrochromic material,the second conductive electrode, and the second glass element. Thediffuse transmitter on the third surface is separated from the reflectorby the second glass element. By incorporating a combinedreflector/electrode on the third surface in accordance with the presentinvention, one of the diffuse transmitters is removed and the distancebetween the reflector and the remaining diffuse transmitter is closer bythe thickness of the rear glass element. Therefore, the third surfacemetal reflector/electrode of the present invention provides anelectrochromic mirror with a superior viewing image.

[0037] Finally, a third surface metal reflector/electrode improves theability to reduce double imaging in an electrochromic mirror. As statedabove, there are several interfaces where reflections can occur. Some ofthese reflections can be significantly reduced with color suppression oranti-reflective coatings; however, the most significant “double imaging”reflections are caused by misalignment of the first surface and thesurface containing the reflector, and the most reproducible way ofminimizing the impact of this reflection is by ensuring both glasselements are parallel. Presently, convex glass is often used for thepassenger side and aspheric glass is sometimes used for the driver sidemirror to increase the field of view and reduce potential blind spots.However, it is difficult to reproducibly bend successive elements ofglass having identical radii of curvature. Therefore, when building anelectrochromic mirror, the front glass element and the rear glasselement may not be perfectly parallel (do not have identical radii ofcurvature) and, therefore, the otherwise controlled double imagingproblems become much more pronounced. By incorporating a combinedreflector electrode on the third surface of the device in accordancewith the present invention, light does not have to travel through therear glass element before being reflected, and any double imaging thatoccurs from the elements being out of parallel will be significantlyreduced.

[0038] It is desirable in the construction of outside rearview mirrorsto incorporate thinner glass in order to decrease the overall weight ofthe mirror so that the mechanisms used to manipulate the orientation ofthe mirror are not overloaded. Decreasing the weight of the device alsoimproves the dynamic stability of the mirror assembly when exposed tovibrations. Heretofore, no electrochromic mirrors incorporating asolution-phase electrochromic medium and two thin glass elements havebeen commercially available because thin glass suffers from beingflexible and prone to warpage or breakage, especially when exposed toextreme environments. This problem is substantially improved by using animproved electrochromic device incorporating two thin glass elementshaving an improved gel material. This improved device is disclosed incommonly assigned U.S. Pat. No. 5,940,201 entitled “ELECTROCHROMICMIRROR WITH TWO THIN GLASS ELEMENTS AND A GELLED ELECTROCHROMIC MEDIUM,”filed on Apr. 2, 1997. The entire disclosure of this U.S. Patent ishereby incorporated herein by reference. The addition of the combinedreflector/electrode onto the third surface of the device further helpsremove any residual double imaging resulting from the two glass elementsbeing out of parallel.

[0039] The most important factors for obtaining a reliableelectrochromic mirror having a third surface reflector/electrode 120 arethat the reflector/electrode has sufficient reflectance and that themirror incorporating the reflector/electrode has adequate operationallife. Regarding reflectance, the auto manufacturers require a highlyreflective mirror for the inside mirror having a minimum reflectivity ofat least 70 percent, whereas the reflectivity requirements for anoutside mirrors are less stringent and generally must be at least 50percent. To produce an electrochromic mirror with 70 percent,reflectance the reflector must have a higher reflectance because havingthe electrochromic medium in contact with the reflector will reduce thereflectance from that interface as compared to having the reflector inair due to the medium having a higher index of refraction as compared toair. Also, the glass, the transparent electrode, and the electrochromicmedium even in its clear state are slightly light absorbing. Typically,if an overall reflectance of 70 percent is desired, the reflector musthave a reflectance of about 80 percent. Therefore, highly reflectance inthe context of the present invention means a reflector whose reflectancein air is at least 80 percent.

[0040] Regarding operational life, the layer or layers that comprise thereflector/electrode 120 must have adequate bond strength to theperipheral seal, the outermost layer must have good shelf life betweenthe time it is coated and the time the mirror is assembled, the layer orlayers must be resistant to atmospheric and electrical contactcorrosion, and must bond well to the glass surface or to other layersdisposed beneath it, e.g., the base or intermediate layer (122 or 123,respectively). The overall sheet resistance for the reflector/electrode120 may range from about 0.01 Ω/□ to about 20 Ω/□ and preferably rangesfrom about 0.2 Ω/□ to about 6 Ω/□. As will be discussed in more detailbelow, improved electrical interconnections using a portion of the thirdsurface reflector/electrode as a high conductance contact or buss barfor the second surface transparent conductive electrode may be utilizedwhen the conductance of the third surface reflector/electrode is belowabout 2 Ω/□.

[0041] Referring to FIG. 3 for one embodiment of the present invention,a reflector/electrodes that is made from a single layer of a highlyreflective silver alloy 121 is provided that is in contact with at leastone solution-phase electrochromic material. The layer of silver alloycovers the entire third surface 114 a of second element 114, providedthat a section of the reflector/electrode may be removed for a displaydevice and a glare sensor, in accordance with U.S. Pat. No. 5,825,527entitled “INFORMATION DISPLAY AREA ON ELECTROCHROMIC MIRRORS HAVING ATHIRD SURFACE REFLECTOR” and filed on Apr. 2, 1997. This application ishereby incorporated in its entirety herein by reference. The highlyreflective silver alloy means a homogeneous or non-homogeneous mixtureof silver and one or more metals, or an unsaturated, saturated, orsupersaturated solid solution of silver and one or more metals. Thethickness of highly reflective layer 121 ranges from about 50 Å to about2000 Å and more preferably from about 200 Å to about 1000 Å. If highlyreflective layer 121 is disposed directly to the glass surface, it ispreferred that the glass surface be treated by plasma discharge toimprove adhesion.

[0042] Table 1 shows the relevant properties for a number of differentmetals that have been proposed for third surface reflectors as comparedwith the materials suitable for the reflector/electrode 120 of thepresent invention. The only materials in Table 1 having reflectanceproperties suitable for use as a third surface reflector/electrode incontact with at least one solution-phase electrochromic material for aninside electrochromic mirror for a motor vehicle are aluminum, silver,and silver alloys. Aluminum performs very poorly when in contact withsolution-phase material(s) in the electrochromic medium because aluminumreacts with or is corroded by these materials. The reacted or corrodedaluminum is non-reflective and non-conductive and will typicallydissolve off, flake off, or delaminate from the glass surface. Silver ismore stable than aluminum but can fail when deposited over the entirethird surface because it does not have long shelf life and is notresistant to electrical contact corrosion when exposed to theenvironmental extremes found in the motor vehicle environment. Theseenvironmental extremes include temperatures ranging from about −40° C.to about 85° C., and humidities ranging from about 0 percent to about100 percent. Further, mirrors must survive at these temperatures andhumidities for coloration cycle lives up to 100,000 cycles. The otherprior art materials (silver/copper, chromium, stainless steel, rhodium,platinum, palladium, Inconel®, copper or titanium) suffer from any oneof a number of deficiencies such as: very poor color neutrality(silver/copper and copper); poor reflectance (chromium, stainless steel,rhodium, platinum, palladium, Inconel®, and titanium); or poorcleanability (chromium).

[0043] When silver is alloyed with certain materials to produce a thirdsurface reflector/electrode, the deficiencies associated with silvermetal and aluminum metal can be overcome. Suitable materials for thereflective layer are alloys of silver/palladium, silver/gold,silver/platinum, silver/rhodium, silver/titanium, etc. The amount of thesolute material, i.e., palladium, gold, etc., can vary. As can be seenfrom Table 1, the silver alloys surprisingly retain the high reflectanceand low sheet resistance properties of silver, while simultaneouslyimproving their contact stability, shelf life, and also increasing theirwindow of potential stability when used as electrodes in propylenecarbonate containing 0.2 molar tetraethylammonium tetrafluoroborate. Thepresently preferred materials for highly reflective layer 121 are Ag/Au,Ag/Pt and Ag/Pd.

[0044] More typically, reflector/electrode 120 has, in addition to thelayer of a highly reflective alloy 121, an optional base layer of aconductive metal or alloy 122 deposited directly on the third surface114 a. There may also be an optional intermediate layer of a conductivemetal or alloy 123 disposed between the layer of highly reflectivematerial 121 and the base coat 122. If reflector/electrode 120 includesmore than one layer, there should not be galvanic corrosion between thetwo metals or alloys. If optional base layer 122 is deposited betweenthe highly reflective layer 121 and the glass element 114, it should beenvironmentally rugged, e.g., bond well to the third (glass) surface 114a and to highly reflective layer 121, and maintain this bond when theseal 116 is bonded to the reflective layer. Base layer 122 should have athickness from about 50 Å to about 2000 Å and more preferably from about100 Å to about 1000 Å. Suitable materials for the base layer 122 arechromium, stainless steel, titanium, and alloys ofchromium/molybdenum/nickel, molybdenum and nickel-based alloys (commonlyreferred to as Inconel®, available from Castle Metals, Chicago, Ill.).The main constituents of Inconel® are nickel which may range from 52percent to 76 percent (Inconel® 617 and 600, respectfully), iron whichmay range from 1.5 percent to 18.5 percent (Inconel® 617 and Inconel®718, respectfully) and chromium which may range from 15 percent to 23percent (Inconel® 600 and Inconel® 601, respectfully). Inconel® 617having 52 percent nickel, 1.5 percent iron, 22 percent chromium, andtypical “other” constituents including 12.5 percent cobalt, 9.0 percentmolybdenum and 1.2 percent aluminum was used in the present examples.

[0045] In some instances it is desirable to provide an optionalintermediate layer 123 between the highly reflective layer 121 and thebase layer 122 in case the material of layer 121 does not adhere well tothe material of layer 122 or there are any adverse interactions betweenthe materials, e.g., galvanic corrosion. If used, intermediate layer 123should exhibit environmental ruggedness, e.g., bond well to the baselayer 122 and to the highly reflective layer 121, and maintain this bondwhen the seal member 116 is bonded to the highly reflective layer 121.The thickness of intermediate layer 123 ranges from about 50 Å to about2000 Å and more preferably from about 100 Å to about 1000 Å. Suitablematerials for the optional intermediate layer 123 are molybdenum,rhodium, stainless steel, titanium, copper, nickel, and platinum.Reference is made to examples 1 and 2 to show how the insertion of arhodium intermediate layer between a chromium base layer and a silver orsilver alloy reflective layer increases the time to failure incopper-accelerated acetic acid-salt spray (CASS) by a factor of 10.Example 4 shows how the insertion of a molybdenum intermediate layerbetween a chromium base layer and a silver alloy having a molybdenumflash over-coat layer increases the time to failure in CASS by a factorof 12.

[0046] Finally, it is sometimes desirable to provide an optional flashover-coat 124 over highly reflective layer 121 such that it (and not thehighly reflective layer 121) contacts the electrochromic medium. Thisflash over-coat layer 124 must have stable behavior as an electrode, itmust have good shelf life, it must bond well to the highly reflectivelayer 121 and maintain this bond when the seal member 116 is bondedthereto. It must be sufficiently thin such that it does not completelyblock the reflectivity of highly reflective layer 121. In accordancewith another embodiment of the present invention, when a very thin flashover-coat 124 is placed over the highly reflective layer, then thehighly reflective layer 121 may be silver metal or a silver alloybecause the flash layer protects the highly reflective layer while stillallowing the highly reflective layer 121 to contribute to thereflectivity of the mirror. In such cases, a thin (between about 25 Åand about 300 Å) layer of rhodium, platinum or molybdenum is depositedover the highly reflective layer 121.

[0047] It is preferred but not essential that the third surfacereflector/electrode 120 be maintained as the cathode in the circuitrybecause this eliminates the possibility of anodic dissolution or anodiccorrosion that might occur if the reflector/electrode was used as theanode. Although as can be seen in Table 1, if certain silver alloys areused the positive potential limit of stability extends out far enough,e.g., 1.2 V, that the silver alloy reflector/electrode could safely beused as the anode in contact with at least one solution-phaseelectrochromic material. TABLE 1 White Light Reflectance NegativePotential Limit Positive Potential Limit Reflectance In Device Contactof Window of Potential Window of Potential Metal In Air (%) StabilityStability (V) Stability (V) Al >92 N/A very poor N/A N/A Cr 65 N/A poorN/A N/A Stainless 60 N/A good N/A N/A Steel Rh 75 N/A very good N/A N/APt 72 N/A very good N/A N/A Inconel 55 N/A N/A N/A N/A Ag 97 84 fair−2.29 0.86 Ag2.7Pd 93 81 good −2.26 0.87 Ag10Pd 80 68 good −2.05 0.97Ag6Pt 92 80 good −1.66* 0.91 Ag6Au 96 84 good −2.25 0.98 Ag15Au 94 82good −2.3 1.2

[0048] The various layers of reflector/electrode 120 can be deposited bya variety of deposition procedures, such as RF and DC sputtering, e-beamevaporation, chemical vapor deposition, electrodeposition, etc., thatwill be known to those skilled in the art. The preferred alloys arepreferably deposited by sputtering (RF or DC) a target of the desiredalloy or by sputtering separate targets of the individual metals thatmake up the desired alloy such that the metals mix during the depositionprocess and the desired alloy is produced when the mixed metals depositand solidify on the substrate surface.

[0049] In another embodiment, the reflector/electrode 120, shown in FIG.4, has at least two layers (121 and 122) where at least one layer of abase material 122 covers the entire portion of the third surface 114 a(except for sections removed for a display device and a glare sensor inaccordance with the U.S. Pat. No. 5,825,527 entitled “INFORMATIONDISPLAY AREA ON ELECTROCHROMIC MIRRORS HAVING A THIRD SURFACEREFLECTOR”) and at least one layer of a highly reflective material 121covers the inner section of the third surface 114 a but does not coverthe peripheral edge portion 125 where seal member 116 is disposed.Peripheral portion 125 may be created by masking that portion of layer122 during deposition of the layer of highly reflective material 121, orthe layer of highly reflective material may be deposited over the entirethird surface and subsequently removed or partially removed in theperipheral portion. The masking of layer 122 may be accomplished by useof a physical mask or through other well-known techniques such asphotolithography and the like. Alternatively, layer 121 may be partiallyremoved in the peripheral portion by a variety of techniques, such as,for example, by etching (laser, chemical or otherwise), mechanicalscraping, sandblasting or otherwise. Laser etching is the presentlypreferred method because of its accuracy, speed and control. Partialremoval is preferably accomplished by laser etching in a pattern whereenough metal is removed to allow the seal member 116 to bond directly tothe third surface 114 a while leaving enough metal in this area suchthat the conductance in this area is not significantly reduced. Forexample, the metal may be removed in a dot pattern or other pattern astaught for removal of metal for information display in the immediatelyabove-referenced U.S. Pat. No. 5,827,527.

[0050] In addition, an optional intermediate layer of a conductivematerial 123 may be placed over the entire area of third surface 114 aand disposed between the highly reflective layer 121 and the base layer122, or it may be placed only under the area covered by layer 121, i.e.,not in peripheral edge portion 125. If this optional intermediate layeris utilized, it can cover the entire area of third surface 114 a or itmay be masked or removed from peripheral edge portion 125 as discussedabove.

[0051] An optional flash over-coat layer 124 may be coated over thehighly reflective layer 121. The highly reflective layer 121, theoptional intermediate layer 123, and the base layer 122 preferably haveproperties similar to that described above, except that the layer ofhighly reflective material 121 need not bond well to the epoxy sealsince it is removed in the peripheral portion where seal member is 116placed. Because the interaction with the epoxy seal is removed, silvermetal itself, in addition to the alloys of silver described above, willfunction as the highly reflective layer.

[0052] Referring again to FIG. 3, chamber 125, defined by transparentconductor 128 (disposed on front element rear surface 112 b),reflector/electrode 120 (disposed on rear element front surface 114 a),and an inner circumferential wall 132 of sealing member 116, contains anelectrochromic medium 126. Electrochromic medium 126 is capable ofattenuating light traveling therethrough and has at least onesolution-phase electrochromic material in intimate contact withreflector/electrode 120 and at least one additional electroactivematerial that may be solution-phase, surface-confined, or one thatplates out onto a surface. However, the presently preferred media aresolution-phase redox electrochromics, such as those disclosed inabove-referenced U.S. Pat. Nos. 4,902,108, 5,128,799, 5,278,693,5,280,380, 5,282,077, 5,294,376, and 5,336,448. Co-filed U.S. Pat. No.6,020,987 entitled “AN IMPROVED ELECTROCHROMIC MEDIUM CAPABLE OFPRODUCING A PRE-SELECTED COLOR” discloses electrochromic media that areperceived to be gray throughout their normal range of operation. Theentire disclosure of this application is hereby incorporated herein byreference. If a solution-phase electrochromic medium is utilized, it maybe inserted into chamber 125 through a sealable fill port 142 throughwell-known techniques, such as vacuum backfilling and the like.

[0053] A resistive heater 138, disposed on the fourth glass surface 114b, may optionally be a layer of ITO, fluorine-doped tin oxide, or may beother heater layers or structures well known in the art. Electricallyconductive spring clips 134 a and 134 b are placed on the coated glasssheets (112 and 114) to make electrical contact with the exposed areasof the transparent conductive coating 128 (clip 134 b) and the thirdsurface reflector/electrode 120 (clip 134 a). Suitable electricalconductors (not shown) may be soldered or otherwise connected to thespring clips (134 a and 134 b) so that a desired voltage may be appliedto the device from a suitable power source.

[0054] An electrical circuit 150, such as those taught in theabove-referenced Canadian Patent No. 1,300,945 and U.S. Pat. Nos.5,204,778, 5,434,407, and 5,451,822, is connected to, and allows controlof the potential to be applied across, reflector/electrode 120 andtransparent electrode 128 such that electrochromic medium 126 willdarken and thereby attenuate various amounts of light travelingtherethrough and thus vary the reflectance of the mirror containingelectrochromic medium 126.

[0055] As stated above, the low resistance of reflector/electrode 120allows greater design flexibility by allowing the electrical contact forthe third surface reflector/electrode to be small while maintainingadequate coloring speed. This flexibility extends to improving theinterconnection techniques to the layer of transparent conductivematerial 128 on the second surface 112 b. Referring now to FIGS. 5a and5 b, an improved mechanism for applying a drive potential to the layerof transparent conductive material 128 is shown. Electrical connectionbetween the power supply and the layer of transparent conductivematerial 128 is made by connecting the buss bars (or clips 119 a) to thearea of reflector/electrode 120 a such that the drive potential travelsthrough the area of reflector/electrode 120 a and the conductiveparticles 116 b in sealing member 116 before reaching the transparentconductor 128. Reflector/electrode must not be present in area 120 c sothat there is no chance of current flow from reflector/electrode area120 a to 120 b. This configuration is advantageous in that it allowsconnection to the transparent conductive material 128 nearly all the wayaround the circumference and therefore improves the speed of dimming andclearing of the electrochromic media 126.

[0056] In such a configuration, sealing member 116 comprises a typicalsealing material, e.g., epoxy 116 a, with conductive particles 116 bcontained therein. The conductive particles may be small, such as, forexample, gold, silver, copper, etc., coated plastic with a diameterranging from about 5 microns to about 80 microns, in which case theremust be a sufficient number of particles to ensure sufficientconductivity between the reflector/electrode area 120 a and thetransparent conductive material 128. Alternatively, the conductiveparticles may be large enough to act as spacers, such as, for example,gold, silver, copper, etc., coated glass or plastic beads. Thereflector/electrode 120 is separated into two distinctreflector/electrode areas (120 a and 120 b, separated by an area 120 cdevoid of reflector/electrode). There are many methods of removing thereflector/electrode 120 from area 120 c, such as, for example, chemicaletching, laser ablating, physical removal by scraping, etc. Depositionin area 120 c can also be avoided by use of a mask during deposition ofreflector/electrode. Sealing member 116 with particles 116 b contactsarea 120 a such that there is a conductive path betweenreflector/electrode area 120 a and the layer of transparent conductivematerial 128. Thus, electrical connection to the reflector/electrodearea 120 b that imparts a potential to the electrochromic medium isconnected through clips 119 b to the electronic circuitry atreflector/electrode area 120 d (FIG. 5b). No conductive particles 116 bcan be placed in this reflector/electrode area 120 b because of thepossibility of an electrical short between reflector/electrode area 120b and the layer of transparent conductive material 128. If such anelectrical short occurred, the electrochromic device would not operateproperly. Additionally, no conductive seal 116 b should be present inarea 120 d.

[0057] A variety of methods can be used to ensure that no conductiveparticles 116 b enter into this reflector/electrode area 120 b, such as,for example, disposing a nonconductive material into the area 120 c ofreflector/electrode devoid of conductive material. A dual dispensercould be used to deposit the seal 116 with conductive particles 116 bonto reflector/electrode area 120 a and simultaneously deposit thenonconductive material into reflector/electrode area 120 c. Anothermethod would be to cure a nonconductive seal in area 120 c and thendispose a conductive material 116 c into the edge gap to electricallyinterconnect reflector/electrode area 120 a with transparent conductivelayer 128. A general method of ensuring that no conductive particlesreach reflector/electrode area 120 b is to make sure seal 116 has properflow characteristics such that the conductive portion 116 b tents tostay behind as the sealant is squeezed out during assembly and only thenon-conductive portion of 116 flows into area 120 b. In an alternativeembodiment, spacer member 116 need not contain conductive particles anda conductive member or material 116 c may be placed on or in the outeredge of member 116 to interconnect transparent conductive material 128to reflector/electrode area 120 a.

[0058] Yet another embodiment of an improved electrical interconnectiontechnique is illustrated in FIG. 6 where a first portion of seal member116 is applied directly onto the third surface 114 a and cured prior tothe application of reflector/electrode 120. After thereflector/electrode 120 is deposited onto the third surface 114 a overthe first portion of seal member 116, a portion of the cured seal member116 is machined off to leave 116 i as shown with a predeterminedthickness (which will vary depending on the desired cell spacing betweenthe second surface 112 b and the third surface 114 a). The cell spacingranges from about 20 microns to about 400 microns, and preferably rangefrom about 90 microns to about 230 microns. By curing the first portionof seal member and machining it to a predetermined thickness (116 i),the need for glass beads to ensure a constant cell spacing iseliminated. Glass beads are useful to provide cell spacing, however,they provide stress points where they contact reflector/electrode 120and transparent conductor 128. By removing the glass beads these stresspoints are also removed. During the machining, the reflector/electrode120 that is coated on the first portion of seal member 116 is removed toleave an area devoid of reflector/electrode 120. A second portion ofseal member 116 ii is then deposited onto the machined area of the firstportion of seal member 116 i or on the coatings on second surface 112 bin the area corresponding to 116 i, and seal member 116 ii is curedafter assembly in a conventional manner. Finally, an outer conductiveseal member 117 may optionally be deposited on the outer peripheralportion of seal member 116 to make electrical contact between the outeredge of reflector/electrode 120 and the outer peripheral edge of thelayer of transparent conductive material 128. This configuration isadvantageous in that it allows connection to the transparent conductivematerial 128 nearly all the way around the circumference and thereforeimproves the speed of dimming and clearing of the electrochromic media126.

[0059] Referring again to FIG. 2, rearview mirrors embodying the presentinvention preferably include a bezel 144, which extends around theentire periphery of each individual assembly 110, 111 a, and/or 111 b.The bezel 144 conceals and protects the spring clips 134 a and 134 b ofFIG. 3, (or 116 a and 116 b of FIG. 5a, 116 i, 116 ii and 117 of FIG. 6)and the peripheral edge portions of sealing member and both the frontand rear glass elements (112 and 114, respectively). A wide variety ofbezel designs are well known in the art, such as, for example, the bezeltaught and claimed in above-referenced U.S. Pat. No. 5,448,397. Thereare also a wide variety of housing well known in the art for attachingthe mirror assembly 110 to the inside front windshield of an automobile,or for attaching the mirror assemblies 111 a and 111 b to the outside ofan automobile. A preferred mounting bracket is disclosed inabove-referenced U.S. Pat. No. 5,337,948.

[0060] The electrical circuit preferably incorporates an ambient lightsensor (not shown) and a glare light sensor 160, the glare light sensorbeing positioned either behind the mirror glass and looking through asection of the mirror with the reflective material completely orpartially removed, or the glare light sensor can be positioned outsidethe reflective surfaces, e.g., in the bezel 144. Additionally, an areaor areas of the electrode and reflector, such as 146, may be completelyremoved, or partially removed in, for example, a dot or line pattern, topermit a vacuum fluorescent display, such as a compass, clock, or otherindicia to show through to the driver of the vehicle. Above-referencedU.S. Pat. No. 5,825,527 entitled “INFORMATION DISPLAY AREA ONELECTROCHROMIC MIRRORS HAVING A THIRD SURFACE REFLECTOR” shows apresently preferred line pattern. The present invention is alsoapplicable to a mirror which uses only one video chip light sensor tomeasure both glare and ambient light and which is further capable ofdetermining the direction of glare. An automatic mirror on the inside ofa vehicle, constructed according to this invention, can also control oneor both outside mirrors as slaves in an automatic mirror system

[0061] The following illustrative examples are not intended to limit thescope of the present invention but to illustrate its application anduse:

EXAMPLE 1

[0062] Electrochromic mirror devices incorporating a high reflectivitythird surface reflector/electrode were prepared by sequentiallydepositing approximately 700 angstroms of chromium and approximately 500angstroms of silver on the surface of 2.3 millimeter thick sheets offlat soda lime float glass cut to an automotive mirror element shape. Asecond set of high reflectivity third surface reflector/electrodes werealso prepared by sequentially depositing 700 angstroms of chromium andapproximately 500 angstroms of a silver alloy containing 3 percent byweight palladium on the glass element shapes. The deposition wasaccomplished by passing the said glass element shapes past separatemetal targets in a magnetron sputtering system with a base pressure of3×10⁻⁶ torr and an argon pressure of 3×10⁻³ torr.

[0063] The chromium/silver and chromium/silver 3 percent palladium alloycoated glass automotive mirror shapes were used as the rear planarelements of an electrochromic mirror device. The front element was asheet of TEC 15 transparent conductor coated glass from LOF cut similarin shape and size to the rear glass element. The front and rear elementswere bonded together by an epoxy perimeter seal with the conductiveplanar surfaces facing each other and parallel to each other with anoffset. The spacing between the electrodes was about 137 microns. Thedevices were vacuum filled through a fill port left in the perimeterseal with an electrochromic solution made up of:

[0064] 0.028 molar 5,10-dihydro-5-10-dimethylphenazine

[0065] 0.034 molar 1,1′-di(3-phenyl(n-propane))-4,4′-bipyridiniumdi(tetrafluoroborate)

[0066] 0.030 molar 2-(2′-hydroxy-5′-methylphenyl)-benzotriazole

[0067] in a solution of 3 weight percent Elvacite™ 2051polymethylmethacrylate resin dissolved in propylene carbonate.

[0068] The fill port was plugged with a UV cure adhesive which was curedby exposure to UV light.

[0069] The devices were subjected to accelerated durability tests untilthe seal integrity of the device was breached or the lamination of thereflector/electrode layers or the transparent electrode layers wassubstantially degraded or dilapidated at which time the said device issaid to fail. The first test performed was steam autoclave testing inwhich the devices were sealed in a water-containing vessel and subjectedto 120° C. at a pressure of 15 pounds per square inch (psi). The secondtest performed was copper-accelerated acetic acid-salt spray (CASS) asdescribed in ASTM B 368-85.

[0070] When the electrochroric devices were observed after one day intesting, all of the devices failed to withstand the CASS testing and allof the devices failed to withstand the steam autoclave testing.

EXAMPLE 2

[0071] Other than as specifically mentioned, the devices in this examplewere constructed in accordance with the conditions and teachings inExample 1. Multilayer combination reflector/electrodes were prepared bysequentially depositing approximately 700 angstroms chromium,approximately 100 angstroms rhodium, and approximately 500 angstroms ofsilver on the surface of said glass element shapes. A second set ofmultilayer combination reflector/electrodes were also prepared bysequentially depositing approximately 700 angstroms of chromium,approximately 100 angstroms rhodium, and approximately 500 angstroms ofa silver alloy containing 3 percent by weight palladium on the surfaceof said glass element shapes. The electrochromic devices wereconstructed and tested in accordance with Example 1.

[0072] The device incorporating the sequential multilayer combinationreflector electrode of chromium, rhodium, and silver withstood steamautoclave testing two times longer and CASS testing 10 times longer thanthe device in Example 1 before failure occurred. The deviceincorporating the sequential multilayer combination reflector electrodeof chromium, rhodium, and silver 3 percent palladium alloy withstoodsteam autoclave testing three times longer and CASS testing 10 timeslonger than devices in Example 1 before failure occurred.

EXAMPLE 3

[0073] Other than as specifically mentioned, the devices in this examplewere constructed in accordance with the conditions and teachings inExample 1. Multilayer combination reflector/electrodes were prepared bysequentially depositing approximately 700 angstroms chromium,approximately 500 angstroms molybdenum, and approximately 500 angstromsof a silver alloy containing 3 percent by weight palladium on thesurface of said glass element shapes. The electrochromic devices wereconstructed and tested in accordance with Example 1.

[0074] The device incorporating the sequential multilayer combinationreflector electrode of chromium, molybdenum, and silver 3 percentpalladium alloy withstood CASS testing 10 times longer than devices inExample 1 before failure occurred.

EXAMPLE 4

[0075] Other than as specifically mentioned, the devices in this examplewere constructed in accordance with the conditions and teachings inExample 1. Multilayer combination reflector/electrodes were prepared bysequentially depositing approximately 700 angstroms chromium,approximately 500 angstroms of a silver alloy containing 3 percent byweight palladium, and approximately 100 angstroms of molybdenum on thesurface of said glass element shapes. A second set of multilayercombination reflector/electrodes were also prepared by sequentiallydepositing approximately 700 angstroms of chromium, approximately 500angstroms molybdenum, approximately 500 angstroms of a silver alloycontaining 3 percent by weight palladium, and approximately 100angstroms of molybdenum on the surface of said glass element shapes. Theelectrochromic devices were constructed and tested in accordance withExample 1.

[0076] The device incorporating the sequential multilayer combinationreflector electrode of chromium, molybdenum, silver 3 percent palladium,molybdenum withstood steam autoclave testing 25 percent longer and CASStesting twelve times longer than the sequential multilayer combinationreflector electrode device of chromium, silver 3 percent palladium,molybdenum before failure occurred. Also, the device incorporating thesequential multilayer combination reflector electrode of chromium,molybdenum, silver 3 percent palladium, molybdenum withstood CASStesting three times longer than the device constructed in Example 3.Finally, the sequential multilayer combination reflector electrodedevice of chromium, silver 3 percent palladium, molybdenum withstood twotimes longer in CASS testing and twenty times longer in steam autoclavetesting than the sequential multilayer combination reflector electrodedevice of chromium, silver 3 percent palladium of Example 1.

EXAMPLE 5

[0077] Other than as specifically mentioned, the devices in this examplewere constructed in accordance with the conditions and teachings inExample 1. Multilayer combination reflector/electrodes were prepared bysequentially depositing approximately 700 angstroms chromium,approximately 100 angstroms rhodium, and approximately 500 angstroms ofsilver on the surface of said glass element shapes. A second set ofmultilayer combination reflector/electrodes were also prepared bysequentially depositing approximately 700 angstroms of chromium,approximately 100 angstroms rhodium and approximately 500 angstroms of asilver alloy containing 3 percent by weight palladium on the surface ofsaid glass element shapes. A third set of multilayer combinationreflector/electrodes were also prepared by sequentially depositingapproximately 700 angstroms of chromium, approximately 100 angstromsrhodium and approximately 500 angstroms of a silver alloy containing 6percent by weight platinum on the surface of said glass element shapes.A fourth set of multilayer combination reflector/electrodes were alsoprepared by sequentially depositing approximately 700 angstroms ofchromium, approximately 100 angstroms rhodium and approximately 500angstroms of a silver alloy containing 6 percent by weight gold on thesurface of said glass element shapes. A fifth set of multilayercombination reflector/electrodes were also prepared by sequentiallydepositing approximately 700 angstroms of chromium, approximately 100angstroms rhodium and approximately 500 angstroms of a silver alloycontaining 15 percent by weight gold on the surface of said glasselement shapes. The electrochromic devices were constructed inaccordance with Example 1.

[0078] Conductive clips were connected to the offset portions of thefront and rear elements of the devices. A power source was connected tothe clips and 1.2 volts were applied to the devices continuously forapproximately 250 hours at approximately 20° C., with the connectionarranged such that the reflector/electrode was the cathode. The deviceincorporating the sequential multilayer combination reflector electrodeof chromium, rhodium, and silver exhibited a yellowing effect within theelectrochromic medium. This yellowing phenomenon was not apparent in anyof the silver alloy devices.

[0079] While the invention has been described in detail herein inaccordance with certain preferred embodiments thereof, manymodifications and changes therein may be effected by those skilled inthe art without departing from the spirit of the invention. Accordingly,it is our intent to be limited only by the scope of the appending claimsand not by way of the details and instrumentalities describing theembodiments shown herein.

The invention claimed is:
 1. An electrochromic device comprising: afront element; a rear element; a seal provided to form a sealed chamber,the sealed chamber being between said elements; and an electrochromicmaterial disposed in said chamber, wherein said seal comprises an epoxyresin at least partially cured with bis(aminocyclohexyl) methane.
 2. Theelectrochromic device of claim 1, wherein said epoxy resin is abisphenol A epoxy resin.
 3. The electrochromic device of claim 2,wherein said bisphenol A epoxy resin is selected from the groupconsisting of Epon 828, Epon 813, Epon 825, Epon 830, and DER
 317. 4.The electrochromic device of claim 1, wherein said epoxy resin is abisphenol F epoxy resin.
 5. The electrochromic device of claim 4,wherein said bisphenol F epoxy resin is selected from the groupconsisting of Epon 862 and PY
 307. 6. The electrochromic device of claim1, wherein said epoxy resin is an epoxy novolac resin.
 7. Theelectrochromic device of claim 6, wherein said epoxy novolac resin is anepoxy phenolic novolac resin.
 8. The electrochromic device of claim 7,wherein said epoxy phenolic novolac resin is selected from the groupconsisting of Epon DPS-155, DEN 431, DEN 438, DEN 439, DEN 444, EPN1138, and EPN
 1139. 9. The electrochromic device of claim 6, whereinsaid epoxy novolac resin is an epoxy cresyl novolac resin.
 10. Theelectrochromic device of claim 9, wherein said epoxy cresyl novolacresin is Epon
 164. 11. The electrochromic device of claim 1, whereinsaid epoxy resin is a glycidyl benzenamine.
 12. The electrochromicdevice of claim 11, wherein said glycidyl benzenamine is selected fromthe group consisting of Ciba MY-720, Ciba MY-0500, and Ciba MY-0510. 13.The electrochromic device of claim 11, wherein said glycidyl benzenamineis tetraglycidyl methylenebisbenzenamine.
 14. The electrochromic deviceof claim 13, wherein said tetraglycidyl methylenebisbenzenamine is CibaMY-720.
 15. A rearview mirror assembly for a vehicle comprising theelectrochromic device of claim 1, and a reflector disposed on a surfaceof said rear element.
 16. An electrochromic device comprising: a frontelement; a rear element; a seal provided to form a sealed chamber, thesealed chamber being between said elements; and an electrochromicmaterial disposed in said chamber, wherein said seal comprises an epoxyresin at least partially cured with a cycloaliphatic amine.
 17. Theelectrochromic device of claim 16, wherein said epoxy resin is abisphenol A epoxy resin.
 18. The electrochromic device of claim 17,wherein said bisphenol A epoxy resin is selected from the groupconsisting of Epon 828, Epon 813, Epon 825, Epon 830, and DER
 317. 19.The electrochromic device of claim 16, wherein said epoxy resin is abisphenol F epoxy resin.
 20. The electrochromic device of claim 19,wherein said bisphenol F epoxy resin is selected from the groupconsisting of Epon 862 and PY
 307. 21. The electrochromic device ofclaim 16 where epoxy resin is an epoxy novolac resin.
 22. Theelectrochromic device of claim 21, wherein said epoxy novolac resin isan epoxy phenolic novolac resin.
 23. The electrochromic device of claim22, wherein said epoxy phenolic novolac resin is selected from the groupconsisting of Epon DPS-155, DEN 431, DEN 438, DEN 439, DEN 444, EPN1138, and EPN
 1139. 24. The electrochromic device of claim 21, whereinsaid epoxy novolac resin is an epoxy cresyl novolac resin.
 25. Theelectroclromic device of claim 24, wherein said epoxy cresyl novolacresin is Epon
 164. 26. The electrochromic device of claim 16, whereinsaid epoxy resin is a glycidyl benzenamine.
 27. The electrochromicdevice of claim 26, wherein said glycidyl benzenamine is selected fromthe group consisting of Ciba MY-720, Ciba MY-0500, and Ciba MY-0510. 28.The electrochromic device of claim 26, wherein said glycidyl benzenamineis tetraglycidyl methylenebisbenzenamine.
 29. The electrochromic deviceof claim 28, wherein said tetraglycidyl methylenebisbenzenamine is CibaMY-720.
 30. The electrochromic device of claim 16, wherein saidcycloaliphatic amine is a bis(cycloaliphatic) amine.
 31. Theelectrochromic device of claim 16, wherein said cycloaliphatic amine isa bis(aminocyclohexyl) methane.
 32. A rearview mirror assembly for avehicle comprising the electrochromic device of claim 16, and areflector disposed on a surface of said rear element.
 33. Anelectrochromic device comprising: a front element; a rear element; aseal provided to form a sealed chamber, the sealed chamber being betweensaid elements; and an electrochromic material disposed in said chamber,wherein said seal comprises an epoxy resin at least partially cured witha cycloaliphatic amine.
 34. The electrochromic device of claim 33,wherein said epoxy resin is a (bisphenol A) epoxy resin.
 35. Theelectrochromic device of claim 34, wherein said bisphenol A epoxy resinis selected from the group consisting of Epon 828, Epon 813, Epon 825,Epon 830, and DER
 317. 36. The electrochromic device of claim 33,wherein said epoxy resin is a bisphenol F epoxy resin.
 37. Theelectrochromic device of claim 36, wherein said bisphenol F epoxy resinis selected from the group consisting of Epon 862 and PY
 307. 38. Theelectrochromic device of claim 33 where epoxy resin is an epoxy novolacresin.
 39. The electrochromic device of claim 38, wherein said epoxynovolac resin is an epoxy phenolic novolac resin.
 40. The electrochromicdevice of claim 39, wherein said epoxy phenolic novolac resin isselected from the group consisting of Epon DPS-155, DEN 431, DEN 438,DEN 439, DEN 444, EPN 1138, and EPN
 1139. 41. The electrochromic deviceof claim 38, wherein said epoxy novolac resin is an epoxy cresyl novolacresin.
 42. The electrochromic device of claim 41, wherein said epoxycresyl novolac resin is Epon
 164. 43. The electrochromic device of claim33, wherein said epoxy resin is a glycidyl benzenamine.
 44. Theelectrochromic device of claim 43, wherein said glycidyl benzenamine isselected from the group consisting of Ciba MY-720, Ciba MY-0500, andCiba MY-0510.
 45. The electrochromic device of claim 43, wherein saidglycidyl benzenamine is tetraglycidyl methylenebisbenzenamine.
 46. Theelectrochromic device of claim 45, wherein said tetraglycidylmethylenebisbenzenamine is Ciba MY-720.
 47. The electrochromic device ofclaim 33, wherein said cycloaliphatic amine is a bis(cycloaliphatic)amine.
 48. The electrochromic device of claim 33, wherein saidcycloaliphatic amine is a bis(aminocyclohexyl) methane.
 49. A rearviewmirror assembly for a vehicle comprising the electrochromic device ofclaim 33, and a reflector disposed on a surface of said rear element.50. An electrochromic device comprising: a front element; a rearelement; a seal provided to form a sealed chamber, the sealed chamberbeing between said elements; and an electrochromic material disposed insaid chamber, wherein said seal comprises an epoxy phenolic novolacresin at least partially cured with a bis(aminocyclohexyl) methane. 51.The electrochromic device of claim 50, wherein said epoxy phenolicnovolac resin is selected from the group consisting of Epon DPS-155, DEN431, and EPN
 1138. 52. A rearview mirror assembly for a vehiclecomprising the electrochromic device of claim 50, and a reflectordisposed on a surface of said rear element.
 53. An electrochromic devicecomprising: a front element; a rear element; a seal provided to form asealed chamber, the sealed chamber being between said elements; and anelectrochromic material disposed in said chamber, wherein said sealcomprises DEN 431 epoxy phenolic novolac resin at least partially curedwith a bis(aminocyclohexyl) methane.
 54. A rearview mirror assembly fora vehicle comprising the electrochromic device of claim 53, and areflector disposed on a surface of said rear element.